reserve k for Nat;
reserve p for Prime;

theorem Th1:
  p < 3 implies p = 2
  proof
    assume p < 3;
    then p < 2+1;
    then
A1: p <= 2 by NAT_1:13;
    1 < p by INT_2:def 4;
    then 1+1 <= p by NAT_1:13;
    hence thesis by A1,XXREAL_0:1;
  end;
